Dental casting machine



June10, 1941. BERGER 2,245,065

DENTAL CASTING MACHINE Filed Sept. 28, 1938 2 Sheets-Sheet 1 when RBerger.

June 10, 1941. R ER 1 2,245,065

DENTAL CASTING MACHINE Filed Sept. 2a, 1938 2 sheets-sheet 2 Herbert 1?.Berger- Patented June 10, 1941 UNITED STATES LPATENT OFFICE I DENTALCASIING MACHINE Herbert R. Berger, Brooklyn, N. .Y., asslxnor to J. F.Jelenko & 00., Inc., New York, N. Y.

Application September 28, 1938, Serial No. 232,207

The present invention relates to improvements 4 7 Claims.

in casting apparatus of the type capable of use in dental and'jewelrywork, or similar work.

In the casting of metals for dental work, jewelry, and other fine workby the usual centrifugal methods in which visual inspection is relied.upon to determine the proper time for molding, many defects are oftenpresent in the finished castvision of an apparatus of this characterwhich may be manufactured as a complete unit or as an attachment to beapplied to centrifugal machines now in use.

Other objects and advantages of the invention will b apparent during thecourse of the following description.

In the accompanying drawings, which form,a part of this specificationand wherein like characters of reference denote like parts throughout,

Figure 1 is an elevation of a casting apparatus embodying the presentinvention and of the type capable of use with centrifugal apparatus nowin use,

Figure 2 is a top plan view thereof,

Figure 3 is a vertical sectional view taken on the line 3-3 of Figure 1,

Figure 4 is a front elevation of the electrical melting furnace,

Figure 5 is a diagrammatic representation of the electrical circuitsemployed,

Figure 6 is a longitudinal sectional view on an enlarged scale of thefurnace side of th apparatus, and,

Figure 7 is a side elevation of a complete casting apparatus embodyingthe present invention.

In the drawings, wherein for the purpose of illustration is shown apreferred embodiment of i the invention, the numeral l0 designates thebase of a centrifugal casting machine of the type now in use in which acentral vertical shaft H projects above the casing and is connected to aspring motor or other source of power within the casing which is adaptedto rotate the shaft H at high speed. Casings and shafts of this type arein common use with various types of centrlfugal casting machines. Ahorizontal bar I2 is removably secured to the upper end of shaft l I torotate therewith.

A furnace or oven l3 isrigidly secured to the bar 12 by means of a pairof clamping members l4 removably bolted at IE to the bar I! at a pointbetween the shaft and one end of the bar l2. The furnace is supportedabove the bar, and when it is desired to remove the furnace, bolts l5are removed and the furnace and clamp slid from. the bar longitudinallythereof. In order to insure proper location of the furnace, bolts l5extend through suitable openings in the bar. The upper ends of clampmembers H ar removably secured to the outer casing of the furnace bymeans of bolts l6. Clamp members [4 are provided with a pair of arms llwhich extend below bar l2 oneon each side thereof. A panel or contactblock i8 is removably secured between arms I)! by means of suitablebolts 19.

The furnace or oven 13 has an outer metal casing 20 which is cylindricalin shape and closed by end walls 28. A cylindrical refractory muille 22is embedded in the end walls of the furnace and is spaced a substantialdistance from the side walls of casing 20. Electrical resistancewindings 23 encircle the outer periphery of the muflie 22 and arecovered by some suitable insulating material such as alundum cement 24which may in turn be surrounded by magnesia,

26 and 27! are disposed in a vertical row adjacent the inner edge ofcontact block it, projecting a short distance laterally beyond the panelor contact block.

A sliding contact holder comprises a bifurcated holder block 28removably secured to the top of casing ID by means of lateral brackets29 detachably bolted to the casing top. The lower portion of holderblock 28 is shaped to conform to the top of the casing and is secured tobrackets 29 by means of suitable bolts 30. A sliding contact plate 31 isslidably disposed in the bifurcated portion'of the-holder block and maybe moved outwardly against the tension of a coil spring 32 by means of afinger piece or lug 33 extending through an elongated horizontal slot inthe holder block. A cover cap 34 closes the top of ries wires connectedto the contact strips 35 and terminates in a pronged plug 81, the prongsof' which vary in diameter to insure the proper electrical connectionsfor the winding 23 and-thermocouple 25.

The contact carrying plate 8| is usually-in the retracted positionindicated in Figures land 6. When the bar I2 is revolved towind up thespring in casing l0, plate 31 is moved outwardly against the tension ofspring 32 to place contact strips 35 in the path of contact block l8 andcontacts 26 and 21. The pressure of bar [2 and the casing spring willhold the plate 3i in extended position and prevent rotation of bar i2.When it is desired to release bar l2 for rotation, it is moved away fromplate 3| against the tension of the casing spring, allowing spring 32 toretract plate 3|. Bar l2 may then be released to rotate with shaft ll.It will be seen that holder block 28 and sliding contact plate 3| may bereadily attached to bases now in use, by means of the bolts on brackets29.

By reference to Figure 6 it will be front end of the furnace casing isprovided with a circular opening 38 which coincides with the innerperiphery of the muilie 22. A smaller opening 39 is disposed in the rearwall of the furnace casing in concentric relation with the muiile. Adoor 40 fits in opening 38 and is pivoted at ti adjacent the top of thefurnace casing. A transparent window 4} may be arranged in the center ofthe door ill.

A crucible 43 is cylindrical in shape and may be of carbon, alundum orother suitable material. Carbon makes an advantageous crucible forprecious metals because of the reducing atmosphere.

The crucible d3 fits within the mufiie 22 and has a sprue M whichextends through the opening 39 to the gate of the mold G5. The cruciblet3 and door dd are held in place by centrifugal force when the bar I2 isrotated. The inner walls of the crucible taper at their ends to theopening in sprue M. The end of'the crucible opposite the sprue has anopening at therein of substantially less width than the inner peripheryof the crucible and concentric therewith. A slot 61 is The contactstrips 35 are spaced to engage the contacts 26 and 21. A flexible cable38 Cal".

seen that the preferably arranged in the top of the crucible to registerwith the thermocoupla25.

A flask holder 58 is frusto-conical in shape and has a depending legprovided with a slot 59 to slidably receive the bar I2. A removable pin50 in'the end of the bar it normally prevents removal of the holder d8.A flask or mold 65 is arranged between the furnace 2t and the frusto=conical portion of the holder d8. A cradle 5! is provided with a pair'ofdepending legs 52 adapted to straddle the bar i2,'and supports mold 65in position to be engaged by flask holder 38. The

cradle 5! may be lifted vertically from bar i2 for removal, and may beadjusted longitudinally along the bar. Various size cradles are providedto accommodate different molds.

A clamping bolt 53 extends through the bottom of flask holder 58 intoslot 69 and is provided with a handle 5% for easy operation. Inoperation, mold 45 is placed in cradle 5! in engagement with sprue 4B,and flask holder #38 is moved into clamping engagement therewith. Bolt53 is then tightened to lock holder 43 on bar l2. The frusto-conicalshape of the holder 38 assures proper centering of the mold 45. In orderto produce a clamping action on the mold when bolt 511s tightened, slot45 is disposed at a slight angle to a horizontal plane, as indicated inFigure 6, so that tightening of bolt 53 will tilt the holder and movethe top of holder 48 towards the furnace 20 and firmly clamp the mold,as seen in Figure 1. v

. A cylindrical counterweight 55 is provided with a longitudinal slot toslidably receive the bar l2 on the side ofshaft H opposite the furnace.A plate 56 is bolted to the lower side of the weight 55 to close thebottom of the slot therein. A handle member 5'! extends above the weight55 and has a reduced removable shank 58 extending through a verticalbore into the slot. The lower end or head of shank 58 is adapted to bereceived in one of a series of spaced openings 60 in the top of bar l2.A coil spring 59 surrounds the shank within the weight slot and, engagesthe head of the shank to normally force the shank into the openings 60.When it is desired to change the position of weight 55, shank 58 isreleased from openings 60 by raising handle 51 against tension of spring59. The weight handle 51 is also used to rotate the bar l2 and shaft H,as when winding up the spring motor in casing I 0. A removable,supplementary weight 6! has a slot to receive the bar 52 and ahorizontal pin 62 adapted to extend into an opening in weight 55 tointerlock the two weights. Pins 63 on bar l2 limit movement of theweights 6i and 55 and may be detachably secured to the bar.

In Figures 1 to 6,the arm I2 is shown as attached to the usual base ea.In Figure 7 it is shown applied to a base ill which is designed to fitthe new arm and furnace. .The base I0 is formed with a flat top toprovide a more comother figures.

In Figure 5 a diagram of the electric circuits employed is illustrated.A pyrometer P is shown in circuit with thermocouple 25 through contacts35 and 26 while an ammeter A, switch 66 and rheostat or other currentcontrolling device 67 are included in the circuit to the heating coil 23through contacts 35' and 27. Obviously, additional circuits may beadded, by merely increasing the number of contacts.

In operation, the handle 57 is graspedand the bar 82 rotated to wind upthe spring motor in casing id or i02 The slidable contact plate Si isthen moved out into the path of contact block l8 against the tension ofthe spring 32. The pressure of the spring motor forces contact blockfirmly against plate 35 and retains it in extended position. Thecircuits to the heating coil and thermocouple are connected throughcontacts 35, 26 and 27 in this position of plate 3!. The mold 65 is thenclamped in position, metal is placed in the crucible and the currentturned on. When the desired temperature is reached, as determined byreference to the pyrometer, handle 51 is grasped and bar, i2 moved toseparate contact 45 under the action of centrifugal force. By the use ofthermocouple 25 and pyrometer P the desired temperature may be obtainedbefore rotating arm l2, without relying upon visual inspection, andcastings of a fine, uniform character may be obtained. The crucible"Imay be removed for cooling by opening door 40 and lifting out thecrucible with a pair of tongs. l

The flask holder 48 may be adjusted to clamp molds of various sizeswhile the counterweights may be adjusted to properly balance the bar i2.The inclined slot 49 insures a lflrm clamping of to without departingfrom the spirit of the inven-" tion or the scope of the subjoinedclaims.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

' being an elongated slot in the upper wall of the crucible to connectthe exterior of the crucible with the interior thereof.

4. In a centrifugal casting machine, means I forming a cylindricalheating chamber and comprising opposite end walls provided with acharging opening and a discharging opening, respectively, said heatingchamber being mounted for rotation about an axis at right angles to thecylinder axis, a cylindrical refractory crucible positioned in saidheating chamber coaxially therewith and provided with opposite endportions adjacent said end walls, respectively, one of said end portionshaving an opening registering with said charging opening, the other ofsaid end portions having an end surface engaging the inner surface ofsaid end wall which is provided with said discharging opening and havingan axially extending part of reduced diameter proecting through saiddischarging opening outwardly beyond said last mentioned end wall andhaving a sprue opening, and a closure movably 1. In a centrifugalcasting machine, a rotary furnace, a muffle disposed within saidfurnace,

an electrical heating element surrounding said muiile, said furnacehaving-a sprue opening on one side and a door on the opposite sidethereof communicating with the muflle, a thermocouple disposed intheupper portion of said muflle, a removable crucible adapted to fitwithin said muille and having a sprue adapted to extend into the sprueopening of the furnace, and said crucible having an elongated slot inits upper portion adapted to register with the thermocouple in themuffle, said thermocouple being positioned externally of the cruciblechamber.

2. In a centrifugal casting machine, a heating chamber having acylindrical muilie, there being a sprue opening in one end of thefurnace and a door in the other end thereof, and a crucible adapted tofit within the mufile, said crucible being of generally cylindricalshape and having a sprue of reduced size adapted to extend into thefurnace sprue opening, the inner walls of said crucible tapering to saidsprue, and said crucible having an opening in its end opposite thesprue, said opening being of less diameter than the inner periphery ofthe crucible whereby a circumferential flange is formed at the end ofthe crucible, and athermocouple in the upper portion of the muflle, saidcrucible being insertable in and. removable from said muflle while saidthermocouple is in position in said muifle, there being a slot in theupper wall of the crucible communicating with the interior of thecrucible and adapted to register with the thermocouple in the muffle.

3. In a centrifugal casting apparatus, a heating chamber, and aremovable crucible adapted to be received in said heating chamber, saidcrucible having a sprueof reduced size at one end thereof, the innerwalls of said crucible tapering to said sprue, saidsprue projectingoutwardly of said heating chamber for engagement with a mold,said-crucible having an opening in its other end opposite the sprue,said opening being of substantial size and of less magnitude than theinner periphery of the crucible whereby a peripheral flange is formed atthe end of the crucible by the end wall defining the crucible opening,and there secured at the charging end of said chamber for closing saidcharging opening and the adjacent opening of said crucible.

. 5. In a centrifugal casting machine, means forming a. cylindricalheating chamber and comprising opposite end walls provided with a charging opening and a discharging opening, respectively, said heatingchamber being mounted for rotation about an axis at right angles to thecylinder axis, a cylindrical refractory crucible wardly beyond said lastmentioned and wall andv having a sprue opening, and a closure movablysecured at the charging end of said chamber for closing said chargingopening and the adjacent opening of said crucible, said crucible beinginsertable in and removable from said heating chamber through saidopening in the charging end of said chamber.

6. In a centrifugal casting machine, means forming a cylindrical heatingchamber and comprising opposite end walls provided with a chargingopening and a discharging opening, respectively, said heating chamberbeing mounted for rotation about an axis at right angles to the cylinderaxis, a cylindrical refractory crucible positioned in said heatingchamber coaxially therewith, and provided with opposite end portionsadjacent said end walls, respectively, one of said end portions havingan opening registering with said charging opening, said crucible havingan inwardly projecting peripheral flange at said end portion thereofwhich is provided with said opening, the other of said end portionshaving an end surface engaging the inner surface of said end wall whichis provided with said discharging opening and having an axiallyextending part of reduced diameter projecting through said dischargingopening outwardly beyond said last mentioned end wall and having a sprueopening,

and a closure movably secured at the charging end of said chamber forclosing said charging 4 aesaoee opening and the adjacent opening of saidcrucihie 7 In a centrifugal casting machine, means forming a cylindricalheating chamber and comprising opposite end walls provided witha charg'ing opening and a discharging opening, respectively, said heatingchamber being mounted for rotation about an axis at right angles to thecylinder axis, a cylindrical refractory crucible positioned in saidheating chamber coaxiaily 1o therewith and provided with opposite endvportions adjacent said end walls, respectively, one of said end portionshaving an opening registering with said charging opening. said cruciblehaving an inwardly projecting peripheral flange at 15 said end portionthereof which is provided with said opening, the other of said endportions having an end surface engaging the inner surface of said endwall which is provided with said dischar-opening and having an axiallyextending part of reduced diameter projecting through said dischargingopening outwardly'beyond said last mentioned end wall and having a sprueopenmg, and a closure movably secured at the charging end oi saidchamber for closing said charging

